This program project proposes to study immunopathogenesis in atopic bronchial asthma with particular emphasis on late phase responses in man and a rabbit model. Changes in specific antibodies of the various immunoglobulin isotypes, relationships of IgA and IgE to the mucus layer, and activation of complement components will be evaluated. Differences between symptomatic and asymptomatic atopic individuals, as well as between atopic and nonatopic individuals, will be studied using longitudinal followup, humoral and cellular responses to specific allergen, and bronchoprovocation. Selected individuals will receive bronchoalveolar lavage for studies of humoral and cellular immunologic parameters in the pulmonary compartment in bronchial asthma. Rabbit models of preferential IgE production will be correlated with longitudinal studies in man including responses to immunotherapeutic maneuvers.